In recent years, along with proliferation of computers and information networking, electronic mail for transmitting/receiving character information through a network is becoming popular. Electronic mail can contain not only a mail text as character information but also files in various formats. For example, a communication apparatus such as an Internet FAX machine which transmits/receives an image by attaching an image file in a TIFF (Tagged Image File Format) format as an attached file has also been proposed.
FIG. 12 is a view showing an arrangement of a conventional electronic mail system including a communication apparatus.
An Internet FAX machine (IFAX) 18, mail client 11, and mail server 12 are connected to a mail server 14, mail client 15, printer 16, and Internet FAX machine (IFAX) 17 through the Internet 13.
Electronic mail software which transmit/receive electronic mail is installed in the mail client 11. In the mail client 11, when electronic mail text data and transmission destination information (e.g., the user name of the mail client 15) are input, and transmission of the electronic mail is instructed, the electronic mail is transmitted to the mail server 12 serving as a POP (Post Office Protocol) server in accordance with the SMTP (Simple Mail Transfer Protocol).
Upon receiving the electronic mail, the mail server 12 determines on the basis of the destination information of the electronic mail data that the transfer destination is the mail server 14 serving as a POP server, and transmits the electronic mail to the mail server 14 through the Internet 13. The mail server 14 receives the electronic mail and stores the received electronic mail in its mail box.
The electronic mail software which transmit/receive electronic mail is also installed in the mail client 15. The mail client 15 checks every predetermined time in accordance with the POP3 (Post Office Protocol Version 3) whether or not new electronic mail has arrived at the mail box of the mail server 14. If new electronic mail has arrived, the electronic mail is downloaded and opened. Thus, the electronic mail text generated by the mail client 11 is displayed. The text or attached file of the electronic mail text can be printed by the printer 16 through a printer driver installed in the mail client 15.
To transmit an image read by the IFAX 17 to the IFAX 18, similarly, the image is transferred through the mail server 14, Internet 13, and mail server 12 and printed by the IFAX 18.
The communication apparatus such as an Internet FAX machine has a transfer function and BOX storage function and therefore can transfer received electronic mail to a designated transfer destination by facsimile, transfer the electronic mail to a third party using an electronic mail protocol, or store the electronic mail in a predetermined recording medium (memory BOX).
In the conventional communication apparatus, when electronic mail is transmitted, it is transferred through a plurality of mail servers. For this reason, even when a transmission error occurs due to an incorrect destination in transmission, the transmission error is not immediately detected. However, when the error is indicated by an intermediate mail server, the mail server that has found the error transmits to the transmission source error notification mail (result report) for notifying the transmission source of the transmission error, so the sender is informed of the error.
However, in the reception mode, since the conventional communication apparatus such as the Internet FAX uses the electronic mail system, not only image data of a TIFF image file but also files that cannot be handled by the Internet FAX machine, e.g., a moving image file or voice data file may be received. In addition, even a TIFF image file may have been compressed by a scheme that cannot be handled by the receiving-side communication apparatus or may be an image file that cannot be handled because the image resolution is high. Even electronic mail data that can be handled by the receiving-side communication apparatus may cause an error due to an error in intermediate mail server or network.
If such electronic mail data that cannot be handled by the receiving-side communication apparatus or electronic mail data having an error is transferred by the transfer function, incorrect data is transferred, resulting in trouble for the receiver. In addition, if the electronic mail data is stored by the BOX storage function, the receiver may be unaware of the error (error in the received mail) or that the mail cannot be handled.
In the transmission mode, when error notification mail (result report) is transmitted, and the above transfer function or BOX storage function is operating at that time, the erroneous mail is transferred or stored. For this reason, the sender can hardly grasp the presence of the erroneous mail and may be unaware of the transmission error.